1. Field of the Invention
The present invention relates generally to chairs and spacers that are used in construction activities for the support of post-tension cables, rebars, or mesh. More particularly, the present invention relates to chairs of plastic construction that are used for the support of such materials in poured decks and precast work. Specifically, the present invention relates to chairs that are used in tilt wall construction.
2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 37 CFR 1.98.
Chairs are commonly used in the construction industry for the support of post-tension cables, rebars, and mesh above a surface. Typically, when such materials are used, they must be supported above the surface when the concrete is poured. Chairs are used with poured decks, precast work, and slab-on-grade applications. In normal use, a receiving area formed on the chair will contact and support the rebar while the base of the chair rests on a deck or on a grade. When the concrete is poured, the chair will support the post-tension cable or rebar a proper distance above the bottom surface.
In deck applications, the most common chair that is employed is a metal chair manufactured by Meadow Steel Products of Tampa, Fla. This chair is made from a pair of bent wires. A first bent wire has a receiving area for the receipt of the rebar. The receiving area is bent into the wire so as to form a generally parabolic indentation. The ends of the wire are bent at a ninety degree angle so as to support the wire in an upright condition above the deck. A second wire is formed in an inverted U-shaped configuration and is welded to the bottom edge of the receiving area of the first wire. The second wire also has ends that are bent at generally ninety degree angles. The first wire will extend in a plane transverse to the second wire such that the first and second wire form the “legs” of the chair. The ends of each of these wires will rest on the deck while the cable is supported. After the concrete has solidified, the deck is removed, and the bottom surfaces of the ends of the wire are exposed. As such, it is necessary to coat the ends of the wires with an anti-rust material. The rebar can be tied to the receiving area.
In normal applications, this Meadow Steel Products' chair will support a single rebar above the deck for a desired distance. However, in other applications, it is often desirable to place a second smaller chair beneath the larger chair so that another additional rebar can be extended so as to intersect with the first rebar. The chairs come in a large number of sizes and heights. In some circumstances, it is often desirable to place more than one rebar into the receiving area of the chair. To accommodate this problem the receiving area of the chair has a generally parabolic indentation.
Corrosion and cost are major problems affecting the Meadow Steel Products' chair. In order to form such a chair, a great deal of manufacturing must take place, including metal forming, bending, dipping, and welding. These activities, along with the cost of the material used to form the chair, make the cost of the chair relatively expensive. If the Meadow steel chair is not coated, then corrosion can adversely affect the product. Such corrosion can occur even on coated metal chairs.
In the past, many attempts have been made to create chairs of plastic material that can serve the purposes of the Meadow Steel Products' chair. In general, such efforts have resulted in plastic chairs that are ineffective, cumbersome to use, or unable to withstand the forces imparted by the cable upon the chair. In some cases, support rings and other structures have been placed upon the plastic chairs so as to give the chair sufficient strength. Unfortunately, as such structures are added to the plastic chair, it becomes increasingly difficult to tie the rebar to the receiving area of the chair. This often requires a threading of the wire through the interior of the plastic chair in order to tie the rebar. As a result of this complicated procedure, many construction workers have been unwilling to use such plastic chairs. Additionally, the interior structures and support rings of such plastic chairs eliminate the ability to extend the rebars in an intersected relationship because one chair cannot be stacked upon or over another.
The plastic chairs of the past have often broken, collapsed, or tipped over in actual use. In the case of the plastic chairs, the base of the chair has only a small area of contact with the deck. Even with the necessary internal structure, experience has shown that such plastic chairs fail to withstand the weight of the rebar.
One particular type of plastic chair that has had some success is manufactured by Aztec Concrete Accessories, Inc. of Fontana, Calif. This chair has a plurality of legs that extend downwardly from a central receiving area. The central receiving area has a generally semi-circular configuration that can receive only a single rebar. An annular ring extends around the legs of the chair so as to provide the necessary structural support for the chair. The feet of the chair extend inwardly of the ring. In use, these chairs have had a tendency to tip over. Additionally, these chairs fail to accommodate the need to align rebars in an intersecting relationship. The use of the annular ring extending around the legs of the chairs requires that a wire must be threaded through the interior of the chair in order to tie the rebar within the receiving area. As such, these chairs have been generally ineffective for meeting the needs of the construction industry. In the past, these and other plastic chairs have been unable to withstand the loads placed upon them. As such, breakage and insufficient rebar support has resulted.
In the past, various U.S. and foreign patents have issued on various devices relating to chairs. For example, U.S. Pat. No. 4,000,591, issued on Jan. 4, 1977, to P. D. Courtois describes a holder adapted for supporting an anchor insert to be embedded into a concrete slab. The holder includes an enclosure, a plurality of legs extending from the enclosure, and a foot at the outer end of each leg adapted with the remaining feet to support the enclosure in a spaced relationship above the floor of a concrete form. The enclosure includes a seat adapted for supporting an insert with the foot of the insert seated thereon. This holder device is not designed supporting rebars in concrete.
British Patent No. 575,043, issued on Jan. 31, 1946, to K. Mattson, teaches a chair-like device that is intended for use in supporting a tendon above the floor of a slab. The support includes a clip formed at the receiving area so as to snap onto the exterior surface of a tendon. Various circular openings are formed in the body of this chair so as to allow tendons to be extended therethrough in parallel and transverse relationship.
Australian Patent No. 227,969, published on Nov. 19, 1959, to Keith Douglas Moris describes a reinforcing chair which includes a plurality of legs extending downwardly from a cruciform receiving area.
Chairs present a particular problem when used in tilt-wall construction. In such circumstances, the chairs are often referred to as “spacers” which are utilized in the forming of the walls of a building by using such concrete tilt-up structures. With prior art metallic rebar chairs, after the concrete wall is poured and properly sets, all spacer and chair locations are checked for exposure of any portion of the chair at the surface of the wall. All of such exposed metallic edges are ground and then sealed to protect from the formation of rust, which attacks the metal of the rebar or chair on the interior of the wall and causes structural weaknesses. In addition, in tilt-wall construction, the metal from the chair can rust and eventually bleed into the concrete of the outer wall. This recreates an unsightly and unprofessional appearance of the concrete structure. As such, a need has developed so as to protect structure from the corrosion of chairs.
A particular problem associated with the use of such plastic chairs in tilt-up construction is the difference in the coefficient of thermal expansion of plastic as opposed to concrete. This is particularly the case when the separate chairs are sprayed with bond breaker compounds prior to the placement of the concrete upon the chairs. Bond breaker compounds are intended to break the seal that can be established between the form boards and concrete used for the formation of the wall. Often, the chairs are sprayed at the same time that the form is sprayed with the bond breaker. As a result, the chair will not adequately adhere directly to the concrete within the structure. Because plastic has a coefficient of expansion greater than the coefficient of expansion of concrete, heat will tend to cause the plastic to expand for a greater distance than the concrete. As a result, the plastic chairs can expand so as to protrude outwardly of the wall subsequent to installation. This is particularly the case when the plastic chair has been coated with a bond breaker compound. As such, a need has developed so as to minimize the expansion of the chair relative to the concrete structure.
The present inventor is also the inventor of the subject matter of U.S. Pat. No. 5,791,095, issued on Aug. 11, 1998, and U.S. Pat. No. 5,555,693, issued on Sep. 17, 1996. Each of these prior patents describes a chair having a receiving area with a horizontal section and generally parabolic section extending transverse to the horizontal section. A plurality of separate legs extend downwardly from the receiving area. Each of the legs has a foot extending horizontally outwardly therefrom. The receiving area on the plurality of legs is integrally formed together of a polymeric material. The horizontal section and the generally parabolic section have a cruciform configuration. Each of the legs has a rectangular cross section in a horizontal plane.
In the chair described in U.S. Pat. Nos. 5,555,693 and 5,791,095 issued to the present inventor, a plurality of small pin members extends downwardly from the bottom surface of each of the feet of the chair. This pin surface has a pointed end and an inward end joined to the underside of the foot. This construction of a pin member created complexities during the injection molding of the chair. For example, the very small spaces used for the formation of such small pin members was difficult to develop. Additionally, because the pin members are directly connected to the underside of the foot, there is no supporting surface extending outwardly from the underside of the foot. As a result, the pointed end of the pin members could easily deflect and could be ineffective in properly grasping the underlying surface. Each of these prior art patents describes the use of three pin members on the underlying surface of each foot. Experiments with the product associated with these patents have indicated that fewer pin members than those indicated in these patents could achieve the same purpose of proper placement and holding capability as the three pin version.
It is an object of the present invention to provide a chair that is corrosion-proof and relatively inexpensive.
It is another object of the present invention to provide a chair that facilitates the ability to stack the chairs.
It is a further object of the present invention to provide a chair that withstands the forces imparted on it.
It is a further object of the present invention to provide a chair that is easy to manufacture and easy to use.
It is still another object of the present invention to provide a chair that has a receiving area that can accommodate several rebars.
It is another object of the present invention to provide a chair with a pin member extending outwardly from a bottom surface of the leg.
It is another object of the present invention to provide a chair which distributes the downward force of the weight of the rebar over a larger surface area.
It is a further object of the present invention to provide a chair for use in tilt-wall construction which minimizes the adverse effects of thermal expansion upon the chair.
It is still a further object of the present invention to provide a chair which resists the adverse effect of the application of bond breaker to the chair.
These and other objects and advantages of the present invention will become apparent from a reading of the attached specification and appended claims.